 /*******************************************************************************
  * Copyright (c) 2005, 2006 IBM Corporation and others. All rights reserved.
  * This program and the accompanying materials are made available under the
  * terms of the Eclipse Public License v1.0 which accompanies this distribution,
  * and is available at http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors: IBM Corporation - initial API and implementation
  ******************************************************************************/
 package org.eclipse.core.resources.mapping;

 import org.eclipse.core.resources.*;
 import org.eclipse.core.runtime.*;

 /**
  * A remote mapping context provides a model element with a view of the remote
  * state of local resources as they relate to a repository operation that is in
  * progress. A repository provider can pass an instance of this interface to a
  * model element when obtaining a set of traversals for a model element. This
  * allows the model element to query the remote state of a resource in order to
  * determine if there are resources that exist remotely but do not exist locally
  * that should be included in the traversal.
  * <p>
  * This class may be subclassed by clients.
  * </p>
  *
  * @see ResourceMapping
  * @see ResourceMappingContext
  * @since 3.2
  */
 public abstract class RemoteResourceMappingContext extends ResourceMappingContext {

     /**
      * Refresh flag constant (bit mask value 1) indicating that the mapping will
      * be making use of the contents of the files covered by the traversals
      * being refreshed.
      */
     public static final int FILE_CONTENTS_REQUIRED = 1;

     /**
      * Refresh flag constant (bit mask value 0) indicating that no additional
      * refresh behavior is required.
      */
     public static final int NONE = 0;

     /**
      * For three-way comparisons, returns an instance of IStorage in order to
      * allow the caller to access the contents of the base resource that
      * corresponds to the given local resource. The base of a resource is the
      * contents of the resource before any local modifications were made. If the
      * base file does not exist, or if this is a two-way comparison, <code>null</code>
      * is returned. The provided local file handle need not exist locally. A exception
      * is thrown if the corresponding base resource is not a file.
      * <p>
      * This method may be long running as a server may need to be contacted to
      * obtain the contents of the file.
      * </p>
      *
      * @param file the local file
      * @param monitor a progress monitor, or <code>null</code> if progress
      * reporting is not desired
      * @return a storage that provides access to the contents of the local
      * resource's corresponding remote resource. If the remote file does not
      * exist, <code>null</code> is returned
      * @exception CoreException if the contents could not be fetched. Reasons
      * include:
      * <ul>
      * <li>The server could not be contacted for some reason.
      * <li>The corresponding remote resource is not a container (status code
      * will be {@link IResourceStatus#RESOURCE_WRONG_TYPE}).</li>
      * </ul>
      */
     public abstract IStorage fetchBaseContents(IFile file, IProgressMonitor monitor) throws CoreException;

     /**
      * Returns the members of the base resource corresponding to the given container.
      * The container and the returned members need not exist locally and may not
      * include all children that exist locally. An empty list is returned if the base resource
      * is empty or does not exist. An exception is thrown if the base resource is not
      * capable of having members. This method returns <code>null</code> if
      * the base members cannot be computed, in which case clients should call
      * {@link #fetchMembers(IContainer, IProgressMonitor)} which returns the
      * combined members for the base and remote.
      * </p>
      * <p>
      * This method may be long running as a server may need to be contacted to
      * obtain the members of the base resource.
      * </p>
      * <p>
      * This default implementation always returns <code>null</code>, but subclasses
      * may override.
      * </p>
      * @param container the local container
      * @param monitor a progress monitor, or <code>null</code> if progress
      * reporting is not desired
      * @return the members of the base resource corresponding to the given container
      * @exception CoreException if the members could not be fetched. Reasons
      * include:
      * <ul>
      * <li>The server could not be contacted for some reason.</li>
      * <li>The base resource is not a container (status code
      * will be {@link IResourceStatus#RESOURCE_WRONG_TYPE}).</li>
      * </ul>
      * @since 3.3
      */
     public IResource[] fetchBaseMembers(IContainer container, IProgressMonitor monitor) throws CoreException {
         if (1 > 2)
             throw new CoreException(Status.OK_STATUS);//avoid compiler warning
 return null;
     }

     /**
      * Returns the combined members of the base and remote resources corresponding
      * to the given container. The container need not exist locally and the result may
      * include entries that do not exist locally and may not include all local
      * children. An empty list is returned if the remote resource which
      * corresponds to the container is empty or if the remote does not exist. An
      * exception is thrown if the corresponding remote is not capable of having
      * members.
      * <p>
      * This method may be long running as a server may need to be contacted to
      * obtain the members of the container's corresponding remote resource.
      * </p>
      *
      * @param container the local container
      * @param monitor a progress monitor, or <code>null</code> if progress
      * reporting is not desired
      * @return returns the combined members of the base and remote resources
      * corresponding to the given container.
      * @exception CoreException if the members could not be fetched. Reasons
      * include:
      * <ul>
      * <li>The server could not be contacted for some reason.</li>
      * <li>The corresponding remote resource is not a container (status code
      * will be {@link IResourceStatus#RESOURCE_WRONG_TYPE}).</li>
      * </ul>
      */
     public abstract IResource[] fetchMembers(IContainer container, IProgressMonitor monitor) throws CoreException;

     /**
      * Returns an instance of IStorage in order to allow the caller to access
      * the contents of the remote that corresponds to the given local resource.
      * If the remote file does not exist, <code>null</code> is returned. The
      * provided local file handle need not exist locally. A exception is thrown
      * if the corresponding remote resource is not a file.
      * <p>
      * This method may be long running as a server may need to be contacted to
      * obtain the contents of the file.
      * </p>
      *
      * @param file the local file
      * @param monitor a progress monitor, or <code>null</code> if progress
      * reporting is not desired
      * @return a storage that provides access to the contents of the local
      * resource's corresponding remote resource. If the remote file does not
      * exist, <code>null</code> is returned
      * @exception CoreException if the contents could not be fetched. Reasons
      * include:
      * <ul>
      * <li>The server could not be contacted for some reason.</li>
      * <li>The corresponding remote resource is not a container (status code
      * will be {@link IResourceStatus#RESOURCE_WRONG_TYPE}).</li>
      * </ul>
      */
     public abstract IStorage fetchRemoteContents(IFile file, IProgressMonitor monitor) throws CoreException;

     /**
      * Returns the members of the remote resource corresponding to the given container.
      * The container and the returned members need not exist locally and may not
      * include all children that exist locally. An empty list is returned if the remote resource
      * is empty or does not exist. An exception is thrown if the remote resource is not
      * capable of having members. This method returns <code>null</code> if
      * the remote members cannot be computed, in which case clients should call
      * {@link #fetchMembers(IContainer, IProgressMonitor)} which returns the
      * combined members for the base and remote.
      * </p>
      * <p>
      * This method may be long running as a server may need to be contacted to
      * obtain the members of the remote resource.
      * </p>
      * <p>
      * This default implementation always returns <code>null</code>, but subclasses
      * may override.
      * </p>
      * @param container the local container
      * @param monitor a progress monitor, or <code>null</code> if progress
      * reporting is not desired
      * @return the members of the remote resource corresponding to the given container
      * @exception CoreException if the members could not be fetched. Reasons
      * include:
      * <ul>
      * <li>The server could not be contacted for some reason.</li>
      * <li>The remote resource is not a container (status code
      * will be {@link IResourceStatus#RESOURCE_WRONG_TYPE}).</li>
      * </ul>
      * @since 3.3
      */
     public IResource[] fetchRemoteMembers(IContainer container, IProgressMonitor monitor) throws CoreException {
         if (1 > 2)
             throw new CoreException(Status.OK_STATUS);//avoid compiler warning
 return null;
     }

     /**
      * Return the list of projects that apply to this context.
      * In other words, the context is only capable of querying the
      * remote state for projects that are contained in the
      * returned list.
      * @return the list of projects that apply to this context
      */
     public abstract IProject[] getProjects();

     /**
      * For three-way comparisons, this method indicates whether local
      * modifications have been made to the given resource. For two-way
      * comparisons, calling this method has the same effect as calling
      * {@link #hasRemoteChange(IResource, IProgressMonitor)}.
      *
      * @param resource the resource being tested
      * @param monitor a progress monitor
      * @return whether the resource contains local modifications
      * @exception CoreException if the contents could not be compared. Reasons
      * include:
      * <ul>
      * <li>The server could not be contacted for some reason.</li>
      * <li>The corresponding remote resource is not a container (status code
      * will be {@link IResourceStatus#RESOURCE_WRONG_TYPE}).</li>
      * </ul>
      */
     public abstract boolean hasLocalChange(IResource resource, IProgressMonitor monitor) throws CoreException;

     /**
      * For two-way comparisons, return whether the contents of the corresponding
      * remote differs from the content of the local file in the context of the
      * current operation. By this we mean that this method will return
      * <code>true</code> if the remote contents differ from the local
      * contents.
      * <p>
      * For three-way comparisons, return whether the contents of the
      * corresponding remote differ from the contents of the base. In other
      * words, this method returns <code>true</code> if the corresponding
      * remote has changed since the last time the local resource was updated
      * with the remote contents.
      * <p>
      * For two-way comparisons, return <code>true</code> if the remote
      * contents differ from the local contents. In this case, this method is
      * equivalent to {@link #hasLocalChange(IResource, IProgressMonitor)}
      * <p>
      * This can be used by clients to determine if they need to fetch the remote
      * contents in order to determine if the resources that constitute the model
      * element are different in the remote location. If the local file exists
      * and the remote file does not, or the remote file exists and the local
      * does not then the contents will be said to differ (i.e. <code>true</code>
      * is returned). Also, implementors will most likely use a timestamp based
      * comparison to determine if the contents differ. This may lead to a
      * situation where <code>true</code> is returned but the actual contents
      * do not differ. Clients must be prepared handle this situation.
      * </p>
      *
      * @param resource the local resource
      * @param monitor a progress monitor, or <code>null</code> if progress
      * reporting is not desired
      * @return whether the contents of the corresponding remote differ from the
      * base.
      * @exception CoreException if the contents could not be compared. Reasons
      * include:
      * <ul>
      * <li>The server could not be contacted for some reason.</li>
      * <li>The corresponding remote resource is not a container (status code
      * will be {@link IResourceStatus#RESOURCE_WRONG_TYPE}).</li>
      * </ul>
      */
     public abstract boolean hasRemoteChange(IResource resource, IProgressMonitor monitor) throws CoreException;

     /**
      * Return <code>true</code> if the context is associated with an operation
      * that is using a three-way comparison and <code>false</code> if it is
      * using a two-way comparison.
      *
      * @return whether the context is a three-way or two-way
      */
     public abstract boolean isThreeWay();

     /**
      * Refresh the known remote state for any resources covered by the given
      * traversals. Clients who require the latest remote state should invoke
      * this method before invoking any others of the class. Mappings can use
      * this method as a hint to the context provider of which resources will be
      * required for the mapping to generate the proper set of traversals.
      * <p>
      * Note that this is really only a hint to the context provider. It is up to
      * implementors to decide, based on the provided traversals, how to
      * efficiently perform the refresh. In the ideal case, calls to
      * {@link #hasRemoteChange(IResource, IProgressMonitor)} and
      * {@link #fetchMembers} would not need to contact the server after a call to a
      * refresh with appropriate traversals. Also, ideally, if
      * {@link #FILE_CONTENTS_REQUIRED} is on of the flags, then the contents
      * for these files will be cached as efficiently as possible so that calls to
      * {@link #fetchRemoteContents} will also not need to contact the server. This
      * may not be possible for all context providers, so clients cannot assume that
      * the above mentioned methods will not be long running. It is still advisable
      * for clients to call {@link #refresh} with as much details as possible since, in
      * the case where a provider is optimized, performance will be much better.
      * </p>
      *
      * @param traversals the resource traversals that indicate which resources
      * are to be refreshed
      * @param flags additional refresh behavior. For instance, if
      * {@link #FILE_CONTENTS_REQUIRED} is one of the flags, this indicates
      * that the client will be accessing the contents of the files covered by
      * the traversals. {@link #NONE} should be used when no additional
      * behavior is required
      * @param monitor a progress monitor, or <code>null</code> if progress
      * reporting is not desired
      * @exception CoreException if the refresh fails. Reasons include:
      * <ul>
      * <li>The server could not be contacted for some reason. </li>
      * </ul>
      */
     public abstract void refresh(ResourceTraversal[] traversals, int flags, IProgressMonitor monitor) throws CoreException;
 }

